Study On The Structural And Magnetic Properties Of Ge/Si Based Diluted Magnetic Semiconductor Films

Today, we need more and more information,and the disadvantage of the conventional semiconductors appears. The transfer and storage of information based on the charge and spin of electron, respectively, could not satisfy the need of people. The diluted magnetic semiconductors (DMSs) simultaneously using both the charge and spin become the most interesting subject. The researchers construct models for theoretic studies. They calculate the Curie temperature, and further study the origin of the magnetism. In experiments, many ferromagnetic DMSs have been obtained. With the combination of theories and experiments, the studies about DMSs have been developing quickly.In this paper, we used magnetron sputtering and ion implantation to prepare codoped films and studied the magnetic properties. Firstly, we prepared Ge_1-xMn_x films by magnetron sputtering, then Fe ions and Co ions were implanted into the Ge_1-xMn_x films by metal vapor vacuum arc, respectively, to obtain two series codoped films. XRD measurements showed that the Ge_1-xMn_x film with low Mn concentration had a Ge cubic structure, but Mn5Ge3 appeared in the Ge0.887Mn0.113 film. The codoped films with Co ions implantation were also Ge cubic structure, and the secondary phase disappeared in the Ge0.887Mn0.113 film. The codoped films with Fe ions implantation were amorphous. The codoped films had different structures. By XPS analysises, the doped Mn existed as Mn0 and Mn₃O₄, which were responsible for the ferromagnetism. In the Co-ion implanted samples, the Mn atoms preferentially occupied the substituted sites. But in the Fe-ion implanted samples, neither Fe nor Mn atoms occupied the substituted sites. The ferromagnetism of the Ge_1-xMn_x films was weakened by the implantation of Co ions, but the saturation magnetization of the codoped films implanted with Fe ions was much larger than that implanted with Co ions. The Fe and Mn codoped Ge based films could be used widely in DMS fields.We prepared Co and N codoped n-Si(100) films, using metal vapor vacuum arc and Kaufman technologies, respectively. XRD measurements showed that the samples were polycrystal Si structures without any secondary phases. The structures of the samples annealed in N2 environment at 800℃for 5 min, did not change. The implanted Co ions existed as Co⁰ by XPS measurements. The saturation magnetization decreased with the increase of implanted dose, and the saturation magnetization decreased after annealing. The implanted Co atoms agglomerated and formed superparamagnetic Co clusters, which resulted in the decrease of the ferromagnetism.